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ESS 101 EXAM 1 with correct answers
nebular hypothesis - CORRECT ANSWERS ✔✔1. supernova and formation of primordial dust cloud
- condensation of primordial dust forms disk shaped nebular cloud rotating counter-clockwise.
- proto sun and planets begin to form
- accretion of planetesimals and differentiation of planets and moons (4-6 billion years ago).
- existing solar system takes shape. Evidence of nebular hypotheses - CORRECT ANSWERS ✔✔1. Planets and moons revolve in a counter-clockwise direction (not random)
- almost all planets and moons rotate on their axis in a counter- clockwise direction.
- planetary orbits are aligned along the suns equatorial plane (not randomly organized)
- observations from Hubble telescope and radio astronomy indicate that other planetary systems are forming from condensed nebular dust. Terrestrial Planets - CORRECT ANSWERS ✔✔Close to the sun, dense, small/rocky, silicate minerals, metallic cores
Twelve earths would fit across the diameter of Jupiter. Jovian Planets - CORRECT ANSWERS ✔✔Far from the sun, low density, large, gaseous (hydrogen, methane) Why does the earth and terrestrial planets have so little molecular hydrogen comprising their respective atmosphere, yet the primordial dust cloud was mostly comprised of hydrogen gas? - CORRECT ANSWERS ✔✔Hydrogen gas and helium gas escapes to space when put in our atmosphere. Jupiter, saturn, and neptune maintain molecular hydrogen gas in the atmosphere because they have high density. Differentiated Earth - CORRECT ANSWERS ✔✔1. Iron Nickel Core (outer core liquid) (inner core solid)
- Fe-Mg silicate mantle
- Fe-Mg-Al Silicate Crust (Ocean and Continental)
- Oceans
- atmosphere How is the earth compositionally zoned? - CORRECT ANSWERS ✔✔Along a density gradient
Why does earth possess little evidence of its early accretion history? - CORRECT ANSWERS ✔✔Because of weathering, plate tectonics, moon has no atmosphere and biosphere. Emissions from degassing of the earth during its differentiation. - CORRECT ANSWERS ✔✔h2o, co2, h2, he, n Where did molecular H and He escape to? - CORRECT ANSWERS ✔✔space When did oxygenation of the atmosphere occur? - CORRECT ANSWERS ✔✔later following evolution of marine algae and plants that use photosynthesis to convert co2 to o2 as a part of their life processes. What layers of the earth can be directly observed? - CORRECT ANSWERS ✔✔crust and uppermost mantle. Evidence of initial composition of the solid earth based on meteorite studies. There are two major classes of meteorites that dominate collected samples. Carbon based meteorites are much rarer, but indicate that the prescursor of life was present early on. - CORRECT ANSWERS ✔✔1. Metallic meteorites (iron nickel density 9.0-10 gm/cm3)
- chondritic meteorites: Fe-Mg silicate, rocky, density is 3.0-3.3)
- carbonaceous chondrites (rare)
What is earths average density? - CORRECT ANSWERS ✔✔5.5 g/cm How can average density of earth be inferred? - CORRECT ANSWERS ✔✔Based on gravitational properties and its effect on known masses such as orbiting satellites. Density of earths crust? - CORRECT ANSWERS ✔✔2.6-3 g/cm density of uppermost mantle? - CORRECT ANSWERS ✔✔3.0-3.3 g/cm Based on the density information, what can you infer about the density of the lower mantle and the earths core? - CORRECT ANSWERS ✔✔Density must be higher than the average. What does the presence of the Earth's magnetic field provide evidence for? - CORRECT ANSWERS ✔✔Earth is likely to possess a metallic core and that a component of this core must be liquid and convecting around the solid metallic portion of the core. Seismic waves - CORRECT ANSWERS ✔✔s and p waves P waves - CORRECT ANSWERS ✔✔Compression waves, velocity: 6- km/sec within lithosphere, propagate through all phases of matter.
What does the s wave being absorbed only at the mantle core boundary tell you about the physical property of the upper mantle? - CORRECT ANSWERS ✔✔It is partially melted. lithosphere - CORRECT ANSWERS ✔✔continental, ocean crust, and uppermost solid mantle Asthenosphere - CORRECT ANSWERS ✔✔upper ductile mantle Low velocity zone - CORRECT ANSWERS ✔✔100-350 km, in the upper mantle that is due to decreasing density. defines the asthenosphere. Why does the density decrease in the region of the upper mantle? - CORRECT ANSWERS ✔✔Because it is undergoing partial melting and has reached its pressure melting temperature. Isostatic equilibrium - CORRECT ANSWERS ✔✔lithosphere "floats" on a partially melted asthenosphere, similar to a raft floating on water. The lithosphere is in isostatic equilibrium with the asthenosphere. Does the thin, dense, ocean lithosphere float lower or higher than the continental lithosphere? - CORRECT ANSWERS ✔✔The ocean
lithosphere floats lower than the continental lithosphere which is less dense (2.6 g/cm3) and thicker (40-70km). What happens when an ice sheet is placed on the lithosphere? - CORRECT ANSWERS ✔✔it will isostatically depress the lithosphere relative to the asthenosphere. When the ice melts, the lithosphere isostatically rebounds. What can plate tectonics explain? - CORRECT ANSWERS ✔✔1. the presence of volcanic mid ocean ridges.
- volcanic mountain chains around the pacific ocean basin.
- the matching coastlines of africa and europe with south america and north america.
- matching ancient rock assemblages of the adjacent continents. ex: climate belts from the Paleozoic aged earth are preserved in the rock record.
- explain the presence of paleozoic aged (300 Ma old) glacial till deposits found in South America, Africa, India, Australia, and Antarctica today.
- the spatial distribution of volcanoes around the world, including the explosive volcanoes rimming the pacific ocean basin (ring of fire).
- explain the spatial distribution of seismic (earthquakes) activity around the world including the depth of their respective foci.
plastic asthenosphere - CORRECT ANSWERS ✔✔composed of the upper mantle and is at or near the melting temperature for upper mantle rock What is the plate tectonic system driven by? - CORRECT ANSWERS ✔✔convection within the asthenosphere. convective upwelling of the asthenosphere along divergent margins produces new ocean lithosphere, while it is subducted along convergent margins. important graph look at on phone or presentation slide - CORRECT ANSWERS ✔✔look at it and memorize it, understand it. two main ways in which melting occurs in the mantle - CORRECT ANSWERS ✔✔look at graph and understand it what is basaltic ocean crust produced by? - CORRECT ANSWERS ✔✔It is produced by partial melting of the garnet-peridotite asthenosphere. As the basaltic magma rises it becomes more fluid (liquid). Why does basaltic magma become more fluid as it rises? - CORRECT ANSWERS ✔✔Think about slope of melting temperature curve with decreasing pressure versus actual temperature curve. Melting temp decreases at a rate greater than actual temp. Actual temp is higher
than melting temp at surface. Why does this occur: when magma reaches surface, its much hotter than the melting temp at surface?? Divergent margins - CORRECT ANSWERS ✔✔first form under continental crust because of the insulating properties. Eventually, the upwelling basaltic magma will completely melt through the overlying continental crust and an incipient ocean basin will form and the two segments of continental crust will rift apart. When the continental crust is first heated at its base what will its topographic expression look like at the surface? - CORRECT ANSWERS ✔✔Think of East africa. It will rise and get higher. sea floor spreading - CORRECT ANSWERS ✔✔The ocean floor becomes wider as the new ocean lithosphere is produced at the divergent margin. What does the east african rift zone represent? - CORRECT ANSWERS ✔✔a continental rift. Why is the topography of east africa highest in the continent? - CORRECT ANSWERS ✔✔because of heating the base of the continent by upwelling basaltic magma. the red sea is an incipient ocean basin. note the dark basalt flows seen along the margins of the red sea in the above satellite image.
seafloor spreading zones. thus it stands to reason that the ocean lithosphere must be consumed along convergent boundaries. Examples of Ocean-Ocean lithosphere convergence (subduction) - CORRECT ANSWERS ✔✔examples are japan and phillipines, examples of ocean continent lithosphere convergence (subduction) - CORRECT ANSWERS ✔✔andes mountains and cascade mountains examples of continent continent lithosphere collision (no subduction) - CORRECT ANSWERS ✔✔examples: himalaya mountains, european alps What are the mechanisms that drive subduction of ocean lithosphere?
- CORRECT ANSWERS ✔✔ridge push, plate sliding, or slab pull. What is the source of rising magma (what components are partially melting?) - CORRECT ANSWERS ✔✔basalt? etc? What is andesite? - CORRECT ANSWERS ✔✔A volcanic rock formed at subduction zones. it has a porphyritic texture (two sizes of crystals related to two staged cooling) When do large crystals form? - CORRECT ANSWERS ✔✔when cooling rate is slow fine matrix when cooling rate is fast.
Why do you think there would be two stages of cooling related to subduction zone volcanism? - CORRECT ANSWERS ✔✔dont know What is the source of magma produced along a continental arc? is this consistent with the similar composition of volcanic rocks collected from Japan and the Cascades? - CORRECT ANSWERS ✔✔continental- continental convergence What kind of volcano is mt. rainier? - CORRECT ANSWERS ✔✔andesitic What collisions are preceded by ocean continental convergence? - CORRECT ANSWERS ✔✔continental collisions Why is it difficult to subduct as the continental lithosphere arrives at the subduction zone? - CORRECT ANSWERS ✔✔because of its low density. What does continental collision cause? - CORRECT ANSWERS ✔✔upwarping and deformation of the ocean floor and ocean lithosphere. even segments of the upper mantle can be squeezed to the surface along the suture zone (where the two continents are stitched together).
Transform boundaries - CORRECT ANSWERS ✔✔typically form along mid ocean rift zones, where the spreading rate differs and the rigid ocean crust is offset along the transform fault. note that plates slide past one another. they produce shear stresses and tarnslational motion where the plates slide past one another. Where are most transform faults located? - CORRECT ANSWERS ✔✔on the ocean floor. they commonly offset active spreading ridges, producing zig zag plate margins and are generally defined by shallow earthquakes. some occur on land. the san andreas fault zone in cali is a transform fault that connects the east pacific rise -a divergent boundary to the south with the south gorda-juan de fuca-explorer ridge, another divergent boundary to the north. the san andreas is one of the few transform faults exposed on land. How can the translational motion of the san andreas transform fault be seen? - CORRECT ANSWERS ✔✔By offset of streams that cross the fault zone Inclination of the earths magnetic field varies over latitude. What is this? - CORRECT ANSWERS ✔✔it is parallel to the surface over the equator and verticl over the magnetic poles. inclination of magnetic minerals from the mt. stuart batholith (located in the north cascades, WA) have low inclinations.
Without a context of plate motions, what would paleomagnetic evidence preserved in the rock record require? - CORRECT ANSWERS ✔✔It would require unique magnetic poles (wandering poles) for different aged rock and locations. What can explain the apparent wandering of the paleomagnetic pole over geologic time? - CORRECT ANSWERS ✔✔movement of tectonic plates including relative movement of continents. what was the precursor to the pacific ocean in the early Triassic period?
- CORRECT ANSWERS ✔✔the pan thalassic ocean Why does Australia have such a unique fauna? - CORRECT ANSWERS ✔✔because they were connected to antarctica, and have unique animals. When did Africa and South America begin to separate? - CORRECT ANSWERS ✔✔dont know what does the separation of africa and south america timing tell you about the evolution of primates relevant to these two continents? - CORRECT ANSWERS ✔✔
What do all minerals have? - CORRECT ANSWERS ✔✔1. specific chemical composition
- specific atomic arrangement (crystal form)
- are solid
- inorganic
- naturally occurring Can minerals form during crystallization of a magmatic melt? - CORRECT ANSWERS ✔✔yes What is basalt composed of? - CORRECT ANSWERS ✔✔minerals that crystallize from magma derived from a partial melt of the asthenosphere. crystals are too small to see with the naked eye. What is andesite composed of? - CORRECT ANSWERS ✔✔minerals that crystallize from magma derived from partial melt of basaltic ocean crust. the large plagliocase crystals cooled slowly underground. Which minerals crystallized first and last from the porphyritic andesite?
- CORRECT ANSWERS ✔✔Big crystals crystallize underground first. Starts underground so big crystals crystallize first. Last to crystallize is c. the gray matrix. Small black minerals crystallize first because it is surrounded by b.
True or false: minerals can precipitate directly from an aqueous (out of water) solution, such as the salt deposits shown in the image above in the desert playa lake. - CORRECT ANSWERS ✔✔true what defines the crystal form of a mineral providing the crystal can grow in an unrestricted environment? - CORRECT ANSWERS ✔✔the arrangement of the atoms , ex: quartz Do you think quartz was the first or last mineral to crystallize in granite? - CORRECT ANSWERS ✔✔last, it has a lower melting temperature. True or false: there are six major crystal systems that may form as constituent atoms arrange themselves during the growth of minerals. What are they? - CORRECT ANSWERS ✔✔True,
- cubic
- tetragonal
- hexagonal
- orthorhombic
- monoclinic
- triclinic What crystal system does sapphire belong to? - CORRECT ANSWERS ✔✔hexagonal?
